急冷塔内喷雾蒸发过程的数值模拟

摘要

The mathematical model of two-phase flow of high temperature flue gas and atomized droplets and heat and mass transfer between two phases were established to prevent the formation of dioxins in the process of cooling.By using computational fluid dynamics ( CFD) method to simulate the evaporation process of atomized droplets which was exist in the quench tower, the effects of inlet flue gas temperature, initial droplet size, initial temperature and injection velocity on the droplet evaporation were analyzed.The simulation results show that droplet evaporation includes two processes:steady state and unsteady state in the steady state, and the droplet equilibrium temperature is affected greatly by the inlet flue gas temperature and with the increase of flue gas temperature.The total evaporation time of droplet group decreases with the increase of flue gas temperature and increases with the increase of initial particle size.The total evaporation time of droplet group is not related to the initial droplet temperature and injection velocity.The initial particle size of 150 microns below can guarantee the 1s cooling flue gas to 200 degrees celsius.The results can provide basis for the design and operation of the quench tower system.%针对废弃物焚烧时高温烟气在降温过程中二噁英的再生成问题,建立了高温烟气与雾化液滴两相流动及两相之间传质传热的数学模型,并以此为基础,利用计算流体力学(CFD)方法对急冷塔内雾化液滴的蒸发过程进行了数值模拟,研究了入口烟气温度、液滴初始粒径、初始温度及喷射速度对液滴群蒸发的影响.模拟结果表明:液滴蒸发经过非稳态和稳态过程,在稳态阶段液滴平衡温度受入口烟气温度的影响较大且随着烟气温度升高而增大;液滴群的完全蒸发时间随着烟气温度的升高而缩短且随着颗粒初始粒径的增大而延长;液滴群完全蒸发时间与液滴初始温度及喷射速度基本无关;初始粒径在150μm以下能保证在1 s内冷却烟气至200℃.该结果可为急冷塔系统设计及运行提供参考.